Office 365 API MVC Authentification

我正在使用MVC Office 365 API库，我想归档以下内容：登录用户帐户，在那里我知道用户名/密码，然后获取日历条目。

到目前为止，我所拥有的是进行重定向并要求用户输入凭据的代码。但是我怎么能在不询问的情况下为他们登录呢？这个想法是每隔几分钟自动获取每个用户（比如说20个用户）的日历条目。

public static async Task<IEvent[]> GetCalendarEvents()
{
    var client = await EnsureClientCreated();
    // Obtain calendar event data
    var eventsResults = await (from i in client.Me.Events
                                where i.End >= DateTimeOffset.UtcNow
                                select i).Take(10).ExecuteAsync();
    var events = eventsResults.CurrentPage.OrderBy(e => e.Start).ToArray();
    return events;
}
public static async Task<ExchangeClient> EnsureClientCreated()
{
    var _discoveryContext = await CacheHelper.GetDiscoveryContext();
    var dcr = await _discoveryContext.DiscoverResourceAsync(ServiceResourceId);
    return new ExchangeClient(ServiceEndpointUri, async () =>
    {
        return (await _discoveryContext.AuthenticationContext.AcquireTokenByRefreshTokenAsync(new SessionCache().Read("RefreshToken"),
            new Microsoft.IdentityModel.Clients.ActiveDirectory.ClientCredential(_discoveryContext.AppIdentity.ClientId, _discoveryContext.AppIdentity.ClientSecret),
            ServiceResourceId))
            .AccessToken;
    });
}